• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Galaxy 2527 (old 2950) super low am modulation

Enterprise312ok

Sr. Member
Jun 12, 2022
523
559
103
36
I have an old 2527 that just won't swing on am. It had q32 removed and tye resistor diode swing mod but that wasn't helping it any so I restored the limiter and removed thw swing mod for now. It will key about 12 watts on am with verry little pep swing. The best swing I can get it to do is 1 watt swinging 2 watts pep on am. The radio wil do about 25 pep on ssb mode. I have checked q51, q54 both finals and driver with compinent tester and all check good.
I have a 2950 service manual and I am going to check all of the electrolytics in that area for shorts.
Any other hints on what to check would be much apreciated.
 

Any other hints on what to check would be much apreciated.
Easiest way to diagnose:
Take another, working radio.
Feed audio from working radio C298 to R298 in defective one. If it will be fine problem is backward to C298. If persist forward from R278. It will narrow search area.
 

Attachments

  • Untitled-1.jpg
    Untitled-1.jpg
    137.2 KB · Views: 18
Easiest way to diagnose:
Take another, working radio.
Feed audio from working radio C298 to R298 in defective one. If it will be fine problem is backward to C298. If persist forward from R278. It will narrow search area.
would it need to be another 2950 type radio or could I use the audio from my Galaxy Dx 2517?
 
I was doing some testing to make sure my previous work before hooking up the test leads and I noticed the am regulator is getting warm if that tells us anything. also l16 I think it is has been adjusted above the top of the can20230311_170958.jpg
 
So, umm. Carrier won't turn up to 4 Watts? Might be time to check L40, L42, L43 and L44 for a proper peak setting. Best way to see a sharp peak on those four is with a steady tone into the mike on sideband (won't matter which) and the mike gain turned down to about 2 Watts. This will make the peak a lot sharper on the meter on those four slugs.

You need to watch for the final resting position of each slug once you're sure it's set for a peak on the wattmeter. See that the top surface of the slug is not DEAD EVEN with the rim of the hole in the can. If you see this, alignment is not the whole story.

Only takes one of those four slugs to be set wrong and reduce your power that much or more. And if you see that "flush with the rim" position on any of those four slugs there's a way around having to replace that can outright.

But for now we'll just skip that.

73
 
This is where a 'scope pays for itself. Seeing how much modulation percentage you have would explain a lot.

73
I have the scope just not a tone generator yet here at the home setup, soon I hope to work my way in to a b&k test set with the signal generator.
 
I did the tx alignment and It did not help much I am getting about 15 watts of either am carrier or ssb out of the rig as is. (was about 25 ssb before I restored q32) Now I have test leads hooked up to the 2527 and I am abut to hook up the 2517 and inject some audio
 
If AM Regulator is getting too hot too quickly - then there is something in the TX strip (or your L16 can area).

Something - when you go into TX mode, slams - and looks for current to power it - as in - overdrive or overdriven section from a previous stage.

Might want to run and observe current with the TX Finals pulled (or disconnected) into a dummy load - with the (+) power lead tied in series on one pole of your test bench supply with an ammeter to check the DRAW in TX and in RX - like what they do (or we do) for those radios that need bias adjusted and have no method to remove jumpers.

Why? - you may have a section in the TX side of things taking too much signal and when filtered out and balanced - is not helping the section that is sending this signal to that filter and balanced out section - it's in overdrive.

Tweak those cans back to where they should be and observe the results - if current begins to climb then dies off - the can your messing with is close (upstream or downstream) from the "problem" section. The rise in current can be caused by the signal peaking then when the stage goes saturated, it can't make more RF - it flattens out - that RF out might be too little to turn on the next stage because of the admittance and filter to take up that stages output is trimming out the unwanted bandwidth but plenty in the DC realm - which only shows the DC pull - the RF side has quit producing.

SO42P mixers are an easy way to show that effect...unbalanced, the RF dies, but ON current for the outputs stay "on" because the DC side is stable - just not amplifying anything because its out of the bandpass.

Because you'll have to do voltage checks and even check for thermal hot spots so you can locate the problem section.
 

dxChat
Help Users
  • No one is chatting at the moment.
  • @ ShadowDelaware:
    AKA- UDX122
  • @ ShadowDelaware:
    West indies and Australia coming in to South Jersey
  • dxBot:
    c316buckeye has left the room.
  • @ nfsus:
    Arkansas skip has been heavy at nights here lately. Australians all over the place
  • dxBot:
    RFactive has left the room.